They will keep indefinitely. There’s two schools of thought when it comes to storage. Some sugar artists recommend keeping them in a shoebox, layered between sheets of tissue paper. It doesn’t hurt to leave the the gel silica packets you find with the shoes inside to suck up any extra moisture. These can be kept in a cool,dry place, away from sunlight. I’ve also had luck storing them in Mason jars and also in plastic Take and Toss-type containers, but I also live in a very dry climate. I would encourage you to experiment a little to find what works best for you. And feel free to post feedback if you find something fantastic for your climate. It definitely helps to have feedback from many different sources!

You might need to wait longer, or just make the petal part and wait until using to add the centers, depending on where you live. Also, drying under a fan can help!

Yes, it’s royal icing, thinned to piping consistency. Here’s a helpful little breakdown: https://www.sweetsugarbelle.com/2012/03/consistency-is-key-twenty-second-icing-and-more/